This allows them to see how the interaction between light and matter creates visible iridescence

Solar cells and biosensors for healthcare could get a major boost from new research that shows how light acts in photonic materials.

The inspiration for this research was the visible iridescence seen in butterfly wings. Researchers wanted to explore how light behaves with matter to make such an extraordinary thing.

The research team, which consisted of scientists from King's College London and European research institutes ICFO in Barcelona and AMOLF in Amsterdam, developed a new technique for observing light and matter's interaction. They had to do this because the limited resolution of an optical microscope has restricted the amount of observation performed in this particular area -- until now.

The technique goes like this: a two-dimensional photonic crystal (nanostructure where two materials with different refractive arrangements are situated in a set pattern) was created using hexagonal holes throughout a silicon nitride sheet. These holes allow certain colors of light to be seen when the photonic crystal's material catches light, but if one hole is left out, the surrounding crystal acts as a "mirror for the light," making this light able to be confined in a small cavity.

Using a new technique based on cathodoluminsescence, where an electron gun creates electrons and shoots them onto a luminescent material to emit light. Each electron creates a burst of light when it hits the material, but the researchers adjusted the technique to work with nanophotonics. In other words, it worked on a much smaller scale -- at a spatial resolution of 30 nanometers to be correct. They were able to see structures at a resolution "10 times smaller than the diffraction limit for light," which showed how the light interacted with matter to create visible iridescence.

"We were thrilled in the lab to observe the finer details of the photonic crystals that were simply inaccessible before," said Dr. Riccardo Sapienza, study leader from King's College London. "This is very important as it allows scientists to test optical theories to a new level of accuracy, fully characterize new optical materials and test new optical devices.

"Our research provides a fundamental insight into light at the nanoscale and, in particular, helps in understanding how light and matter interact. This is the key to advance nanophotonic science and it can be useful to design novel optical devices like enhanced bio-sensors for healthcare, more efficient solar cells and displays or novel quantum optics and information technologies."